The deposition of chromium from a fused fluoride electrolyte

Abstract

The electrodeposition of chromium from a fused fluoride electrolyte (LiFNaFKFCrF 3) was investigated. The electrolyte was prepared simply by oxidizing chromium metal directly into the melt. The chromium reduction mechanism was studied and chromium deposits obtained by both direct and periodically reversed plating were characterized. Flexible deposits of high purity chromium were produced. All deposits eventually deteriorated into particulate and dendritic growths, but periodically reversed plating allowed considerably greater latitude in both film thickness and deposition conditions. The films were initially deposited with a random orientation, but a preferred orientation developed as growth continued. Cathode efficiency measurements suggested that the main reduction process in direct plating involved Cr 3+, whereas in periodically reversed plating there appeared to be a major contribution from Cr 2+. Chronopotentiometry measurements indicated that the chromium was initially deposited with a structure which is different from and transforms into the structure which is observed.